In the AVC (Advanced Video Coding) standard, a scheme called “multi-reference” in which a plurality of reference images are used for motion compensation is employed. By using multi-reference, an optimum reference image can be selected on a macroblock basis. As a result, the coding efficiency can be increased.
In addition, examples of an apparatus that performs AVC coding include a set-top box and a Blu-ray (registered trade name) recorder that convert an MPEG2 (Moving Picture Experts Group phase 2) broadcast bit stream into en AVC bit stream having a low bit rate and accumulate the AVC bit stream in a recording medium.
In order for such apparatuses to compress an HD (High Definition) image at a low bit rate, such as 2 Mbps, while maintaining a high image quality, a variety of innovations are required.
Accordingly, in order to improve the coding efficiency of an encoding apparatus employing multi-reference, a scheme in which reference images are dynamically switched is proposed (refer to, for example, PTL 1).